[RFC PATCH 25/32] fprobe: Use ftrace_regs in fprobe entry handler

Masami Hiramatsu (Google)
2023-11-05T16:11:53Z

From: Masami Hiramatsu (Google) <mhiramat@kernel.org>

This allows fprobes to be available with CONFIG_DYNAMIC_FTRACE_WITH_ARGS
instead of CONFIG_DYNAMIC_FTRACE_WITH_REGS, then we can enable fprobe
on arm64.

Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Acked-by: Florent Revest <revest@chromium.org>
---
Changes from previous series: NOTHING, just forward ported.
---
include/linux/fprobe.h | 2 +-
kernel/trace/Kconfig | 3 ++-
kernel/trace/bpf_trace.c | 10 +++++++---
kernel/trace/fprobe.c | 4 ++--
kernel/trace/trace_fprobe.c | 6 +++++-
lib/test_fprobe.c | 4 ++--
samples/fprobe/fprobe_example.c | 2 +-
7 files changed, 20 insertions(+), 11 deletions(-)

diff --git a/include/linux/fprobe.h b/include/linux/fprobe.h
index 3e03758151f4..36c0595f7b93 100644
--- a/include/linux/fprobe.h
+++ b/include/linux/fprobe.h
@@ -35,7 +35,7 @@ struct fprobe {
int nr_maxactive;

int (*entry_handler)(struct fprobe *fp, unsigned long entry_ip,
- unsigned long ret_ip, struct pt_regs *regs,
+ unsigned long ret_ip, struct ftrace_regs *regs,
void *entry_data);
void (*exit_handler)(struct fprobe *fp, unsigned long entry_ip,
unsigned long ret_ip, struct pt_regs *regs,
diff --git a/kernel/trace/Kconfig b/kernel/trace/Kconfig
index 308b3bec01b1..805d72ab77c6 100644
--- a/kernel/trace/Kconfig
+++ b/kernel/trace/Kconfig
@@ -290,7 +290,7 @@ config DYNAMIC_FTRACE_WITH_ARGS
config FPROBE
bool "Kernel Function Probe (fprobe)"
depends on FUNCTION_TRACER
- depends on DYNAMIC_FTRACE_WITH_REGS
+ depends on DYNAMIC_FTRACE_WITH_REGS || DYNAMIC_FTRACE_WITH_ARGS
depends on HAVE_RETHOOK
select RETHOOK
default n
@@ -675,6 +675,7 @@ config FPROBE_EVENTS
select TRACING
select PROBE_EVENTS
select DYNAMIC_EVENTS
+ depends on DYNAMIC_FTRACE_WITH_REGS
default y
help
This allows user to add tracing events on the function entry and
diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index 868008f56fec..b0b98f0a0e52 100644
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -2501,7 +2501,7 @@ static int __init bpf_event_init(void)
fs_initcall(bpf_event_init);
#endif /* CONFIG_MODULES */

-#ifdef CONFIG_FPROBE
+#if defined(CONFIG_FPROBE) && defined(CONFIG_DYNAMIC_FTRACE_WITH_REGS)
struct bpf_kprobe_multi_link {
struct bpf_link link;
struct fprobe fp;
@@ -2729,10 +2729,14 @@ kprobe_multi_link_prog_run(struct bpf_kprobe_multi_link *link,

static int
kprobe_multi_link_handler(struct fprobe *fp, unsigned long fentry_ip,
- unsigned long ret_ip, struct pt_regs *regs,
+ unsigned long ret_ip, struct ftrace_regs *fregs,
void *data)
{
struct bpf_kprobe_multi_link *link;
+ struct pt_regs *regs = ftrace_get_regs(fregs);
+
+ if (!regs)
+ return 0;

link = container_of(fp, struct bpf_kprobe_multi_link, fp);
kprobe_multi_link_prog_run(link, get_entry_ip(fentry_ip), regs);
@@ -3004,7 +3008,7 @@ int bpf_kprobe_multi_link_attach(const union bpf_attr *attr, struct bpf_prog *pr
kvfree(cookies);
return err;
}
-#else /* !CONFIG_FPROBE */
+#else /* !CONFIG_FPROBE || !CONFIG_DYNAMIC_FTRACE_WITH_REGS */
int bpf_kprobe_multi_link_attach(const union bpf_attr *attr, struct bpf_prog *prog)
{
return -EOPNOTSUPP;
diff --git a/kernel/trace/fprobe.c b/kernel/trace/fprobe.c
index 881f90f0cbcf..df323cb7bed1 100644
--- a/kernel/trace/fprobe.c
+++ b/kernel/trace/fprobe.c
@@ -46,7 +46,7 @@ static inline void __fprobe_handler(unsigned long ip, unsigned long parent_ip,
}

if (fp->entry_handler)
- ret = fp->entry_handler(fp, ip, parent_ip, ftrace_get_regs(fregs), entry_data);
+ ret = fp->entry_handler(fp, ip, parent_ip, fregs, entry_data);

/* If entry_handler returns !0, nmissed is not counted. */
if (rh) {
@@ -182,7 +182,7 @@ static void fprobe_init(struct fprobe *fp)
fp->ops.func = fprobe_kprobe_handler;
else
fp->ops.func = fprobe_handler;
- fp->ops.flags |= FTRACE_OPS_FL_SAVE_REGS;
+ fp->ops.flags |= FTRACE_OPS_FL_SAVE_ARGS;
}

static int fprobe_init_rethook(struct fprobe *fp, int num)
diff --git a/kernel/trace/trace_fprobe.c b/kernel/trace/trace_fprobe.c
index 8bfe23af9c73..71bf38d698f1 100644
--- a/kernel/trace/trace_fprobe.c
+++ b/kernel/trace/trace_fprobe.c
@@ -320,12 +320,16 @@ NOKPROBE_SYMBOL(fexit_perf_func);
#endif /* CONFIG_PERF_EVENTS */

static int fentry_dispatcher(struct fprobe *fp, unsigned long entry_ip,
- unsigned long ret_ip, struct pt_regs *regs,
+ unsigned long ret_ip, struct ftrace_regs *fregs,
void *entry_data)
{
struct trace_fprobe *tf = container_of(fp, struct trace_fprobe, fp);
+ struct pt_regs *regs = ftrace_get_regs(fregs);
int ret = 0;

+ if (!regs)
+ return 0;
+
if (trace_probe_test_flag(&tf->tp, TP_FLAG_TRACE))
fentry_trace_func(tf, entry_ip, regs);
#ifdef CONFIG_PERF_EVENTS
diff --git a/lib/test_fprobe.c b/lib/test_fprobe.c
index 24de0e5ff859..ff607babba18 100644
--- a/lib/test_fprobe.c
+++ b/lib/test_fprobe.c
@@ -40,7 +40,7 @@ static noinline u32 fprobe_selftest_nest_target(u32 value, u32 (*nest)(u32))

static notrace int fp_entry_handler(struct fprobe *fp, unsigned long ip,
unsigned long ret_ip,
- struct pt_regs *regs, void *data)
+ struct ftrace_regs *fregs, void *data)
{
KUNIT_EXPECT_FALSE(current_test, preemptible());
/* This can be called on the fprobe_selftest_target and the fprobe_selftest_target2 */
@@ -81,7 +81,7 @@ static notrace void fp_exit_handler(struct fprobe *fp, unsigned long ip,

static notrace int nest_entry_handler(struct fprobe *fp, unsigned long ip,
unsigned long ret_ip,
- struct pt_regs *regs, void *data)
+ struct ftrace_regs *fregs, void *data)
{
KUNIT_EXPECT_FALSE(current_test, preemptible());
return 0;
diff --git a/samples/fprobe/fprobe_example.c b/samples/fprobe/fprobe_example.c
index 64e715e7ed11..1545a1aac616 100644
--- a/samples/fprobe/fprobe_example.c
+++ b/samples/fprobe/fprobe_example.c
@@ -50,7 +50,7 @@ static void show_backtrace(void)

static int sample_entry_handler(struct fprobe *fp, unsigned long ip,
unsigned long ret_ip,
- struct pt_regs *regs, void *data)
+ struct ftrace_regs *fregs, void *data)
{
if (use_trace)
/*